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Biomedical subjects

M Hawken

Publications and source records attributed to M Hawken.

13 recordsLinked to original sources
PubMed1995

Postural stability differentiates "lower body" from idiopathic parkinsonism.

INTRODUCTION: Patients with an akinetic Parkinson syndrome of the lower extremities and a poor response to L-DOPA have been described as "lower body Parkinsonism" (LBP). These patients are characterized by frequent fallings and poor balance. METHODS: We have studied body sway with static (force platform) and dynamic (Equitest) posturography in 11 LBP patients, 6 of them revealing deep white matter lesions on MRI and 10 patients with advanced Parkinson's disease (PD) and compared performance with 30 age-matched controls. RESULTS: When standing on a fixed support the postural performance of both patient groups lay within the normal range. The balance of LBP patients worsened in the static testing in the conditions "eyes open on foam" (p < 0.05) and "eyes closed on foam" (p < 0.0006, of 11 patients falling), whereas the balance of PD patients deteriorated only with "eyes closed on foam" (p < 0.05). Dynamic posturography confirmed these results in 6 different sensory conditions, clearly distinguishing the more unstable LBP patients from PD patients during "standing, eyes closed, foot support sway referenced" (p < 0.005). CONCLUSION: We conclude, that postural adjustments in LBP patients are more disturbed than those in PD patients and posturography can be an additional tool for the differential diagnosis of Parkinson syndromes with gait disorders.

Aged↗
PubMed1994

Recurrence of HIV-related tuberculosis in an endemic area may be due to relapse or reinfection.

SETTING: Two Research Clinics within Nairobi, Kenya, one in the Infectious Diseases Hospital, the national referral centre for tuberculosis, and one in a community based project in Pumwani district, and the Bacterial Molecular Genetics Unit at the London School of Hygiene and Tropical Medicine. OBJECTIVE: To determine whether recurrence of tuberculosis after 'adequate' treatment was due to reinfection with a different isolate of Mycobacterium tuberculosis or to relapse of the original infection. DESIGN: A retrospective comparison by DNA fingerprinting of sets of isolates of M. tuberculosis from patients with recurrence of tuberculosis and in whom isolates from the original episode had been stored was made. Five patients with recurrence of tuberculosis two to nineteen months after adequate treatment and documented clearance of disease were studied. RESULTS: In one patient, fingerprints of the isolates of M. tuberculosis from the recurrence were quite different to those from the original episode; in the other four, the fingerprints were identical. CONCLUSION: Reinfection rather than relapse was the cause of recurrence in at least one patient. The high 'relapse' rates seen in HIV-related tuberculosis in Africa may in part be due to increased susceptibility to reinfection and not to treatment failure.

AIDS-Related Opportunistic Infections↗
PubMed1993

Increased recurrence of tuberculosis in HIV-1-infected patients in Kenya.

There is evidence that in human immunodeficiency virus 1 (HIV-1) infected patients with tuberculosis the rate of recurrence of tuberculosis is increased in those patients treated with a standard thiacetazone-containing regimen. To assess the impact of HIV-1 on tuberculosis in Kenya, patients with tuberculosis were studied prospectively. After treatment with either a standard thiacetazone plus isoniazid regimen or a short-course thiacetazone-containing regimen, overall recurrence rate of tuberculosis was 34 times greater in 58 HIV-1-positive patients than in 138 HIV-1-negative patients (adjusted rate ratio 33.8, 95% CI 4.3-264). Recurrence in the HIV-1-positive group was strongly associated with a cutaneous hypersensitivity reaction due to thiacetazone during initial treatment (rate ratio 13.2, 95% CI 3.1-56.2). In all patients with a cutaneous hypersensitivity reaction ethambutol was substituted for thiacetazone. No significant association was found between recurrence among HIV-1-positive patients and initial resistance, initial treatment regimen, a diagnosis of AIDS (WHO definition), or poor compliance. DNA fingerprinting suggested that both relapse and new infection may have produced recurrence of tuberculosis. In patients who had a cutaneous hypersensitivity reaction, increased recurrence rate may have been related to interruption of treatment, subsequent poor compliance, or more advanced immunosuppression. Alternatively, a change to the combination of ethambutol and isoniazid in the continuation phase for 11 months only may not be adequate.

AIDS-Related Opportunistic Infections↗
PubMed1992

Intermittent supervised treatment of tuberculosis at Green Lane Hospital, 1987-8.

AIMS: to assess the results of the first two years experience with intermittent supervised treatment of tuberculosis (IST) in Auckland, looking especially at practical problems. METHOD: the hospital records of the 16 patients who received IST during 1987-8 were reviewed retrospectively, and public health nurses who administered the medications were questioned about problems that were encountered. RESULTS: two-thirds of those who were given IST were Polynesian. In retrospect, the need for IST could have been anticipated in eight of the 12 patients (67%) who failed to comply with daily treatment. Five of the 16 IST patients presented major problems to the nurses supervising the twice weekly treatment. Poor motivation, itinerancy and alcohol abuse were the most common factors causing difficulty. IST was successfully completed in 13/16 patients (81%) and was abandoned in only one patient. Only two patients completed IST with a drug regimen for resistant organisms. Health nurse supervision resulted in improvements in understanding and attitude to tuberculosis, eventually enabling two patients to self medicate without supervision. CONCLUSIONS: IST is a practical treatment method in New Zealand, permitting curative therapy in a group of tuberculosis patients who would otherwise create risks of drug resistance, disease reactivation and spreading the disease.

Adult↗
PubMed1987

Human contrast discrimination and the threshold of cortical neurons.

The human contrast-discrimination function has a curious shape: In addition to rising for increasing contrasts, both positive and negative, it also rises for very low contrasts on either side of zero. It is shown that this rise near zero contrast is not much affected by procedures that increase or decrease the subject's knowledge of the stimulus; this counts against uncertainty as the immediate cause of the elevation near zero contrast. The alternative explanation in terms of a genuine response threshold is shown to be promising when measurements of human contrast discrimination are compared with values calculated from records of neurons in monkey primary visual cortex. The comparison also suggests that the dynamic range of single neurons is lower than that shown psychophysically. It is suggested that having a cortical threshold may be the visual system's way of preventing false positives when there is much stimulus uncertainty. This threshold may also help to explain why quantum efficiencies calculated from detection thresholds are so poor compared with those estimated from the visual system's susceptibility to added noise.

Humans↗
PubMed1985

Capabilities of monkey cortical cells in spatial-resolution tasks.

The performance of individual neurons in monkey striate cortex has been examined in three spatial-resolution tasks by making microelectrode recordings from single cells in anaesthetized, paralyzed animals. The statistical reliability of responses from cells was used to estimate threshold levels of performance. For each task (resolution acuity for high-contrast gratings, discrimination of gratings varying in spatial frequency, and localization ability, i.e., discrimination of spatial phase), performance approaching psychophysical thresholds was obtained from single cortical cells. The receptive-field organization underlying localization performance was examined in detail by the use of a linear model that relates localization ability to the sensitivity of the receptive field to luminance contrast. Calculations from this model agree well with direct measurements of localization performance and are comparable with psychophysical measurements of hyperacuity. Though it has been suggested that cells with nonoriented receptive fields in cortical layer IVc beta may be responsible for recovering fine-grain spatial information, our calculations indicate that these cells are poorer at localization than many other cells in the cortex.

Animals↗
PubMedDate not supplied

Dynamic platform sway measurement in Menière's disease.

Fourteen patients in the latent phase of Menière's disease and 14 control subjects were tested on a moving platform apparatus as part of a protocol of investigations for Menière's disease. Subjects were tested under 3 different visual conditions (eyes open, eyes closed, sway feedback) and 2 proprioceptive conditions (fixed platform and ankle stabilization). There was a significant interaction between subject group and visual condition, Menière's patients had a larger RMS sway amplitude than controls with their eyes open and closed, but this difference was abolished by sway feedback. Loss of either visual or proprioceptive sensory information increased sway amplitude, indicating that both cues influence postural control, and in different ways, but patients were able to use these cues to maintain upright posture almost as effectively as controls. More patients than controls lost balance with ankles stabilized and eyes closed, but the difference was not statistically significant (P = 0.0516). There was no detectable relationship between clinical ratings of disease severity and sway scores. The dynamic platform tests described in this report are more suitable for tests involving comparisons between groups of subjects rather than for diagnostic testing of individuals.

Adult↗